Chasmodes needs to answer this question. He gets all kinds of great observations and videos and as near as I can tell, he's pretty darn close to the tanks. As for me I pretty much let myself revel in the interaction with the fishes (even if they're just begging for food) and consider anything natural a bonus if I actually get to see it...
Sorry, for some reason I missed these posts. I've never had a problem with my 20g long tank. The fish in that tank were all raised from juveniles, so they are very used to me. They do beg for food somewhat, but if I don't feed them within a few minutes, they go back to doing what they do as if I'm not there.
But, when I kept fish in my 20g high (same species, blennies, gobies, skilletfish), they were all collected as adults. Every time I approached and sat at the tank, all they would do is approach the front glass and beg for food relentlessly. And this happened also even after I fed them! So, to observe them, I had to find a way to hide so they wouldn't see much of me and forget that I was there. So, I built a hide out of a blanket and towels, using bungie cords for support and closepins, and it worked. I'd enter the room and sit next to the tank, and the fish would go nuts begging for food. Then, I'd clip up the makeshift "hide", and within a few minutes, they'd forget that i was there.
Another thing that I've noticed is that my fish behave differently if the lights are on in the room. If I turn out the room lights so only the tank is lit, then they seem to forget that I'm there (with my 20g long current oyster reef). In my 20g high tank, same thing pretty much, but with the blind. There was enough light from the tank illuminating me that they could still see me. Behind the blind, it was darker. However, if I moved, they'd beg again.
Very cool about the snails. Free healthy food!